This invention relates generally to automatic machines having a head arranged for dispensing strands of composite material onto a surface to fabricate structures.
In particular, present date technology machines have been developed to arrange and compact strands or tows of composite material; for example, untwisted carbon fibers impregnated with epoxy or thermoplastic resin. Machines of this type may be known as AVSD (Advanced Variable Strand Dispensing) machines, wherein the tows are carried on storage creels, and are routed in parallel fashion at predetermined spaced intervals, beneath a compacting roller which compresses the strands against a surface, thus flattening and causing the strands to be contiguous in nature to create a part structure. Subsequent processing steps on such structures may employ a compression mold to further shape and compact the structure and, in the case of thermosetting resins, a curing operation may be performed, utilizing vacuum bags in autoclaves for receiving the molded part.
Some prior art assemblies have difficulty in handling cut strands, because the strands tend to get away and must be rethreaded for the next pass or lay down of material. Further, difficulties are encountered when using a single compacting roller to compress the material. As additional plys of material are built up, the built up structure becomes somewhat compliant to the compacting roller which must compress the next lay down of strands against the built-up structure. Additionally, certain prior art structures propose spacing the strands with a mechanism somewhat removed from the part compacting unit, and it is felt that through this invention better control of the spacing of the composite strands may be accomplished by placing the spacing mechanism closer to the compacting roller and part surface.
Applicant has obviated the difficulties inherent in the prior art assemblies by a novel strand dispensing head, utilizing a precompaction roller assembly running ahead of the compacting roller. Further, applicant has employed a spacing mechanism in a close relationship with a precompaction roller.
Applicant has further provided a novel strand clamping and cutting mechanism after the precompaction roller, which greatly facilitates ease of restarting the lay down procedure.